The aim of the present study was to investigate the C=C conversion and acid-base reaction in modern self-adhesive resin cements.
Method:
The materials tested were: G-CEM LinkAce (GL,GC Int.), Rely-X Ultimate (RL,3M ESPE) and Rely-X Unicem 2 (RN,3M ESPE). The setting reactions were studied by ATR-FTIR spectroscopy. Cement specimens (Ø: 5mm,h:100um,n:6, per material/condition/time interval) were prepared and studied immediately after mixing (0min, control), following 8min, 1h and 3w dark/dry storage (37oC) without light-curing (D series) and for the same time intervals after 10s irradiation (1200 mW/cm2, L series). The amount of remaining C=C bonds (%RDB) was measured employing the two band technique (analytical band:C=C/1636cm-1 for all; reference bands: aromatic C..C/1605cm-1 for RUL,RUN and urethane N-H/1540cm-1 for GLA) and normalized vs the individual controls (0min).For the acid-base reaction the changes in the PO3 sym (~950cm-1) vs the reference band ratios (%RPG)were monitored and normalized by the corresponding control values. 3-way ANOVA and Holm-Sidak tests were used to assess the statistically significant differences (a=0.05)
Result:
No significant differences were found in %RDB among the materials in L mode (means 54.3-57.4%). In D mode the %RDB values were significantly higher than in L mode (66.7-76.0%), with GL demonstrating the lowest mean (3w, 60.4%). At 3w the GL (60.4±2.8%) values showed a significant difference from the rest. For the %RPG, L series showed significantly higher values than D series (50.6-62.7% vs 35.7-49% at 8 min and 1h). The lowest values were found in GL at 3w (D: 8%, L: 12.8%) followed by the rest (D:30.9-34.3%, L:43.5-47.6%)
Conclusion:
There are significant differences in the conversion and acid-base reaction among the products tested. Light-curing enhanced conversion in comparison with chemical-curing in all products, with the smallest difference found in GL after prolonged storage. The same material resulted in the lowest %RPG after prolonged storage.